Heretofore, numerous primary accelerators such as the various well known sulfenamides of 2-mercaptobenzothiazole, and to a lesser extent, sulfenimides of 2-mercaptobenzothiazole [also referred to as bis(sulfenamides)] have been utilized to cure natural and/or synthetic rubbers. While they improved upon the art preceding them, still faster cure rate, longer scorch delay, and better reversion resistance are desirable.
U.S. Pat. No. 2,321,305 to Messer relates to rubber vulcanization accelerators represented by the formula ##STR2## where AR is an arylene group; when n is 1, X is NH-alkyl, NH-aryl, N-diaryl, O-alkyl or O-aryl; when n is 2, X is oxygen, NH, N-alkyl, or N-alicyclic; when n is 3, X is N.
U.S. Pat. No. 2,321,306 to Messer also relates to rubber vulcanization accelerators of the type set forth in U.S. Pat. No. 2,321,305.
U.S. Pat. Nos. 2,860,142 to Conly; 2,873,277 to Sundholm; 2,889,331 to Sundholm; 3,151,122 to Sundholm; and 3,875,177 to Maison, all relate to bis(sulfenamides) (sulfenimides) of 2-mercaptobenzothiazole as accelerators. While referred to in the prior art as bis(sulfenamides), it is chemically correct to refer to these compounds as sulfenimides.